Image displaying system, image displaying device, image data outputting device, image displaying method, image displaying program, and image data outputting program

ABSTRACT

A system consisting of a plurality of terminals storing image data and an image displaying device which are connected with each other through a network capable of two-way communication has the disadvantage of decreasing in throughput on account of slow image data transfer over the network. The image displaying device performs two-way communications with each of the terminals by a communication means at the display device side. Also, the image displaying device acquires image data from a relevant terminal while instructing other terminals to suspend transmission by the image data acquisition controlling means, thereby suspending transmission of image data. The image displaying device displays images by the image displaying means based on the thus acquired image data.

This is a Division of application Ser. No. 10/682,547 filed Oct. 10,2003. The disclosure of the prior application is hereby incorporated byreference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image displaying system, imagedisplaying device, image data outputting device, image displayingmethod, image displaying program, and image data outputting program.

2. Description of the Prior Art

The image displaying system of conventional type consists of an imagedisplaying device and a plurality of terminals connected thereto througha network so that the former displays images in response to image datatransmitted from the latter. (See Japanese Patent Laid-open No.2001-358919, for example.) In such a system, transmission of image datafrom the image data sources to the image displaying device isefficiently accomplished by giving an identifier to each image datasource and allocating the storage areas in the image displaying devicein correspondence with the identifier. Thus, the image data transmittedfrom each image data source is stored in each of the allocated areas.This arrangement permits one image data source to transmit image data tothe image displaying device while the image displaying device isperforming presentation by using the image data transmitted from anotherimage data source. The consequence is efficient transmission of imagedata from a plurality of image data sources and smooth switching ofimage data for presentation. (See Japanese Patent Laid-open No.2001-358919, paragraph 48.)

The conventional image displaying system mentioned above has thedisadvantage of being low in throughput on account of the network. Inother words, the network is limited in the maximum transmission rate,and this poses a problem with transmission. That is, if a plurality ofterminals happen to transmit image data simultaneously, one of them mayfail in adequate transmission or have to repeat transmission on accountof congestion.

SUMMARY OF THE INVENTION

The present invention was completed in view of the foregoing. It is anobject of the present invention to provide an image displaying system,image displaying device, image data outputting device, image displayingmethod, image displaying program, and image data outputting program,which are designed for smooth transmission of image data from aplurality of terminals.

According to the present invention, the above-mentioned object isachieved by connecting an image displaying device with a plurality ofterminals through a network capable of two-way communications such thatwhile a specific terminal is transmitting image data, other terminals donot transmit image data. To this end, the image displaying devicepossesses a means to control the acquisition of image data so as tocause image data sources, except for one specific image data source, tosuspend transmission. Each terminal possesses a means to control theoutput of image data so that it does not output image data upon itsreceipt of an instruction to suspend transmission. Thus, the means tocontrol the output of image data outputs image data unless it receivesan instruction to suspend transmission. In other words, the terminalthat outputs image data is the specific terminal and the means tocontrol the acquisition of image data acquires image data from thespecific terminal.

Thus, at the time of transmission of image data from a plurality ofterminals, the foregoing arrangement makes it possible to restrict theterminal that actually outputs data to the network and the amount ofdata to be output to the network. Needless to say, in the case where aplurality of terminals are the source of transmission of image data,after a specific terminal has finished transmission of image data,another terminal is made a specific terminal. This arrangement permitsall the sources of transmission to transmit image data to the imagedisplaying device while restricting the amount of data to be output tothe network.

Here, any one of the terminals to output image data for display of imageby the image displaying device should become the specific terminal atleast once. The amount of data to be sent to the network may berestricted if there exists only one terminal at all times in thesimplest embodiment of the present invention. However, for a networkwith a high transmission rate, it is acceptable that two or moreterminals are made the specific terminals and they are allowed to outputimage data simultaneously, while other terminals than the specificterminals are suspending transmission of image data. Instruction tosuspend transmission may vary in its form so long as it is addressed tospecific terminals. For example, in the case of packet communications,it may describe the data to specify the recipient terminal at the headerof the data packet and the command to suspend transmission (which isunderstandable by each terminal) as the content of transmission data.

Incidentally, according to the present invention, the image displayingdevice has a communication means at the displaying device side and eachof the terminals has a communication means at the terminal side, so thatthese communication means perform two-way communications. So long asthese communication means permit two-way communications between theimage displaying device and the terminals, they are not specificallyrestricted in communication line, protocol, standard, etc. For example,the communication line may be wire network or wireless network, theprotocol may be TCP or UDP, and the standard may be Ethernet (registeredtrademark of Fuji-Xerox Corp.), IEEE1394, USB, or the like.

The image displaying device may widely vary in its type; it is notspecifically restricted in its way to display images. It may be aprojector (designed to project images to a screen), a plasma display(designed to display images on its built-in screen), a CRT, or a liquidcrystal display. Presentation is one way to display images from aplurality of terminals. Any displaying device capable of displaying alarge image is desirable for presentation. The terminal should be ableto store image data and output it later as required; it may be ageneral-purpose computer or a recording-reproducing device (such asvideo).

The present invention is directed to an image displaying systemconsisting of an image displaying device and a plurality of terminals.The present invention is directed separately to the image displayingdevice and each of the terminals. The image displaying device to displayimages upon acquisition of image data from a plurality of terminalshould desirably be able to switch its operating mode. In one mode, itdisplays on one screen images supplied from a plurality of terminals. Inanother mode, it displays on one screen a single image supplied fromeach terminal separately.

Thus, the image displaying device should be provided with a modeswitching means so that it can switch the split display mode and thesequential display mode from each other according to the user'spreference. The mode switching means may be widely varied. It may be amode switching button attached to the image displaying device proper.Or, it may be a switch capable of remote control. Another possiblearrangement is such that a plurality of terminals issue instruction formode switching. In this case, each terminal sends a mode switchingcommand through the above-mentioned network and the image displayingdevice switches mode as it receives the command.

The split displaying mode permits each of the divided sections of thescreen to display the image based on the individual image data which hasbeen output from a plurality of terminals. This arrangement realizespresentation with a plurality of images. The way of splitting the screenis not specifically restricted; the screen may be equally divided intoidentical panes or unequally divided into a large and small panes. Thenumber of splitting is not specifically restricted. Presentation with aplurality of images does not usually use all the images at one time butswitches the images sequentially in each split section.

According to the present invention, acquisition of images from aplurality of terminals is accomplished in such a way that the imagedisplaying device acquires image data from a specific terminal and then(after it has acquired image data) it acquires image data from anotherterminal. Therefore, if images in split sections are switched one byone, it is possible to prohibit transmission from terminals other thanthat which outputs image data for the image which has been switched.This permits the image displaying device to acquire necessary datarapidly. In this way it is possible to prevent the transmission of imagedata for the image which is not switched. In other words, there is nopossibility that unnecessary data is transmitted over the network.

The sequential display mode is one which displays on a single screen theimage based on image data which has been output from a plurality ofterminals and which switches the image as required. This arrangementrealizes presentation with images which have been output from aplurality of terminals. In this case, too, the image displaying deviceonly acquires the image data for images being displayed and hence theimage data for images not being displayed is not transmitted over thenetwork. Therefore, there is no possibility that unnecessary data istransmitted over the network. This reduces the network load and permitsspeedy acquisition of necessary data. Incidentally, in either mode, theswitching of images may be accomplished by means of a button (on theimage displaying device) or a remote controller.

A desirable split display mode may be constructed such that the imagedisplaying device sequentially acquires image data for the images to bedisplayed on the split sections. In this case, the terminals (or theabove-mentioned specific terminals) which output image data aresequentially switched without suspending the output of image data. Inother words, as one terminal completes the output of image data, theimage displaying device instructs that terminal to suspend transmissionand instructs other terminals not to perform transmission. It is alsopossible to instruct a new specific terminal to start transmissioninstead of instructing to suspend transmission. In this way it ispossible to limit the number of terminals which send data over thenetwork and to permit the image displaying device to acquire image datafor each image to be displayed on the split section while keeping thenetwork load low.

The sequential display mode may be carried out in such a way that theimage displaying device continues to acquire image data until thespecific terminal transmitting image data is switched. As the result,the specific terminal transmits over the network only the image data tobe displayed on the image displaying device. Needless to say, otherterminals, which are not instructed to suspend transmission, continue tooutput image data. Continuance of the acquisition or output of imagedata for still pictures means that the terminal transmits image data forone picture and then waits and transmits again image data for the nextpicture as soon as an instruction to display the next picture is issued.In the case of moving pictures, the output of image data is continueduntil the transmitting terminal is switched. Of course, the transmissionof data is postponed if the amount of image data exceeds the capacity ofthe buffer in the image displaying device.

The image displaying system mentioned above will function if the imagedisplaying device and terminals perform prescribed processingsequentially, as a matter of course. Therefore, the present invention isdirected also to an image displaying method. The displaying systemaccording to the present invention may exist alone or may beincorporated into any apparatus. The present invent embraces all ofthese embodiments, which may manifest themselves as software orhardware.

If the idea of the present invention is embodied in software for theimage displaying system, there exists a program to realize its function,as a matter of course.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing the construction of the image displayingsystem according to the present invention.

FIG. 2 is a flowchart for the process to be carried out in theprojector.

FIG. 3 is a flowchart for the process to be carried out in the computerPC.

FIG. 4 is a diagram illustrating the action of the image displayingsystem.

FIG. 5 is a diagram illustrating the action of the image displayingsystem.

DESCRIPTION OF THE REFERRED EMBODIMENTS

The embodiment of the present invention will be described in the ordershown below.

(1) Construction of the image displaying system

(2) Processing by the projector

(3) Processing by each terminal

(4) Action of the image displaying system

(5) Other embodiments

(1) Construction of the Image Displaying System

FIG. 1 is a diagram showing the construction of the image displayingsystem. In this figure, there is shown the image displaying system 10,which consists of a plurality of computers PC 20 and the projector 30.The projector 30 acquires the image data which has been output from eachcomputer PC 20 and then projects an image for display according to thethus acquired image data. In this embodiment, the computers PC 20 andthe projector 30 communicate with each other through the UTP cable forLAN.

In addition, the computers PC 20 and the projector 30 communicate witheach other by means of TCP protocol. The computers PC 20 and theprojector 30 establish connection by exchanging packets with each other,so that each of image data is transmitted after division into packets,as occasion demands. In FIG. 1, a plurality of computers PC 20 aredesignated as computer PC1 to computer PC4, and the construction of thecomputer PCd is shown by a block diagram. Each of the computers PC2 toPC4 may have the same construction as shown in the block diagram.

The computer PC 20 may be any general-purpose computer capable ofcontrolling the interface and recording media and executing programsunder the control of a specific OS. The computer PC 20 as a constituentof the image displaying system according to the present invention isprovided with a network interface 21, a controller 22, an imagetransmitting module 23, and a hard disk drive (HDD) 24. The controller22 controls the network interface 21 for communication with theprojector 30. In other words, it interprets the command described in thepacket received through the network interface 21, and it transmits andreceives data.

In this embodiment, the controller 22 acquires the request to suspendtransmission, the request to transmit image data for one screen, and therequest to transmit image data continuously, which are sent from theprojector 30. Then, the controller 22 controls the image transmittingmodule 23 and causes it to output image data properly. The HDD 24 is astorage medium capable of storing various data; it stores previouslyprepared image data 24 a for images to be used for presentation. Theimage transmitting module 23 acquires the image data 24 a and outputs itto the projector 30 in response to the instruction from the controller22.

The projector 30 is also capable of controlling the interface andrecording media and executing the prescribed program under control of aspecific OS. The projector 30 as a constituent of the image displayingsystem according to the present invention is provided with a networkinterface 31, a controller 32, an image receiving module 33, an HDD 34,a display 35, and a remote control signal receiver 36. The controller 32controls the network interface 31 for communications with the computerPC 20. In other words, it interprets the command described in the packetreceived through the network interface 31, and it transmits and receivesdata.

In this embodiment, the controller 32 outputs the request to suspendtransmission, the request to transmit image data for one screen, and therequest to transmit image data continuously, which are sent to thecomputer PC 20. This construction permits the acquisition of necessaryimage data while keeping low the amount of data being transmitted overthe network. In addition, the controller 32 controls the image receivingmodule 33, thereby causing it to acquire the image data for one screenor the image data which is continuously transmitted from each computerPC 20. The controller 32 also causes the HDD 34 to store the image data34 a.

The controller 32 controls the display 35, thereby causing it to displayvarious images based on the image data 34 a. In other words, thecontroller 32 determines the brightness of the color of each pixel basedon the data concerning each pixel indicated by the image data 34 a,thereby controlling the display 35. Responding to this control, thedisplay 35 projects light onto an outside screen through the lens,thereby displaying an image. In addition, the controller 32 determinesthe brightness of the color of each pixel of the image on the screen insuch a way that the image on the screen is divided into a plurality ofsections and each section shows the image based on the image data sentfrom each computer PC 20. Of course, the controller 32 may also cause animage to be shown on the entire screen based on the image data sent fromeach computer PC 20.

Incidentally, in this embodiment of the present invention, the projector30 has the remote control signal receiver 36, which receives signalstransmitted from a remote controller (not shown), so that the controller32 understand what is intended by the remote controller. The remotecontroller sends an instruction to switch the image, so that thecontroller 32 switches the image sequentially in response to theinstruction for image switching. In other words, the controller 32instructs the computer PC 20 (as the source of image data) to outputimage data after switching and then acquires image data, thereby causingthe display 35 to display the relevant image. This construction permitsthe user to perform presentation while switching the images by remotecontrol.

In addition, the remote controller permits one to issue an instructionfor mode switching. The projector 30 according to this embodiment hasthe split display mode and the sequential display mode. The splitdisplay mode works in such a way that the controller 32 controls thedisplay 35, thereby dividing one screen into a plurality of sections andcausing each section to display an image based on the image datasupplied from each computer PC 20. In this way the user can carry outpresentation by showing the audience a plurality of images at one time.

In the sequential display mode, images based on the image data which hasbeen output by a plurality of terminals are sequentially displayed onone screen, and the computers PC 20 (as the senders) can be sequentiallyswitched by the remote controller mentioned above. When one of thecomputers PC 20 (as the senders) is switched, the controller 32 suspendscommunications with remaining computers PC 20 and acquires the imagedata only from the relevant computer PC 20 and causes the display todisplay an image. This arrangement permits one to carry out presentationby using image data transmitted from a plurality of computers PC 20while causing them to transmit only necessary image data over thenetwork and keeping the network load low.

(2) Processing by the Projector

What the controller 32 processes in the projector will be described indetail with reference to the flowchart shown in FIG. 2. According tothis embodiment, it is necessary to set up the above-mentioned modebefore starting image projection by the projector 30. It is alsonecessary to previously set up connection with each of the computers PC20 connected to the network. In step S100, the controller 32 judgeswhether or not the number of computers PC 20 with connection establishedthrough the network is one. If the judgment in step S100 is affirmative,the controller 32 controls the image receiving module 33 and carries outcommunications only with one of the computers PC 20 which hasestablished connection. Then, the controller 32 acquires image data onlyfrom the relevant computer PC 20 and causes the display 35 to display animage.

If the judgment in step S100 is not affirmative, the controller 32judges the current mode in step S110. (This judgment indicates that aplurality of computers PC 20 are connected to the network and is capableof communication with the projector 30.) If the result of judgment instep S110 is that the previously established mode is the split displaymode, then the controller 32 outputs a packet to all the computers PC 20which have established connection, instructing to suspend transmission.This action prevents the image data from being output to the networkfrom the computer PC 20.

In step S130, the controller 32 controls the image receiving module 33and requests each of the computers PC 20 to transmit image data. Inother words, the action in the split display mode is to cause each ofthe computers PC 20 to output the images to be displayed on each dividedsection of the screen. Thus, the controller 32 sends a request to thespecific computer 20 for transmission and communicates with only therelevant computer PC 20 to acquire the image data for each dividedsection of the screen and suspend transmission. The controller 32repeats this action as many times as the number of the divided sectionsof the screen. The result is that when the controller 32 acquires theimage data for all the images to be displayed on the divided section, itprevents the computers PC 20 from transmitting data over the networksimultaneously, so that it can acquire image data for the dividedsections while keeping the network load low.

If the result of judgment in step S111 is that the previouslyestablished mode is the sequential mode, then the controller 32 requests(in step 140) all the computers PC, except for the relevant one storingthe image data for the image to be displayed by the projector 30, tosuspend transmission. In step S150, the controller 32 controls the imagereceiving module 33 and sends a request for transmission to the relevantcomputer PC 20 storing the image data for the image to be displayed bythe projector 30, and it communicates only with the relevant computer PC20.

At this time, the image receiving module 33 may acquire the image datafor one image and acquire additional image data each time it receives aninstruction for image switching from the remote control signal receiver36. Alternatively, it may acquire the image data which is continuouslyoutput for reproduction of moving pictures. In either cases, the systemwhich is so constructed as to acquire the image data only from therelevant computer PC 20 prevents a plurality of computers PC 20 fromtransmitting data over the network at one time and hence acquires theimage data while keeping the network load low.

(3) Processing by Each Terminal

What the controller 22 processes in each computer PC 20 will bedescribed in detail with reference to the flow-chart shown in FIG. 3.The controller 22 in each computer PC 20 previously establishesconnection with the above-mentioned projector 30 before the image datais output. And, each computer PC 20 carries out the process shown inFIG. 3 remaining in the state ready for outputting the image data forthe image to be displayed by the projector 30. In step S200, thecontroller 22 monitors the network interface 21. In other words, itjudges whether or not it has received a packet showing any request toitself from the projector 30.

If the controller 22 judges in step S200 that it has received a packetshowing a certain request from the projector 30, then it judges in stepS210 whether or not a request has been issued for suspension oftransmission. If the controller 22 judges in step S210 that a requesthas been issued for suspension of transmission, then it controls theimage transmitting module 23 in step S220 and suspends packettransmission. The computer PC suspends transmission temporarily eventhough it is a terminal to output the image data for an image to bedisplayed on one of the divided sections of the screen, and it waits fortransmission while repeating the process in step S200.

If the controller 22 judges in step S210 that there is no request forsuspension of transmission, then it judges in step S230 whether or notthere is a request for transmission of image data for one image. If thecontroller 22 judges in step S230 that there is a request fortransmission of image data for one image, then it controls the imagetransmitting module 23, thereby causing it to output image data for oneimage in step S240. If the controller judges in step S230 that there isno request for image data for one image, then it judges in step S250whether or not there is a request for continuous transmission of imagedata.

If the controller 22 judges in step S250 that there is a request forcontinuous transmission of image data, then it controls the imagetransmitting module 23, thereby causing it to transmit image datacontinuously in step S260. According to this embodiment, the controller22 previously judges in step S210 whether or not there is a request forsuspension of transmission. Because of the above-mentioned processing,the computer PC 20, except for the one which has received a request fortransmission, waits for trans-mission of image data until it receives arequest for transmission. Therefore, the controller 22 causes onlynecessary data to be output over the network while keeping the networkload low.

(4) Action of the Image Displaying System

The above-mentioned construction and processing realizes the imagedisplaying system which functions as illustrated in FIG. 4. Theembodiment shown in FIG. 5 is based on the split display mode. Thescreen is divided into four nearly identical sections, on which aredisplayed the images corresponding to the image data output from thecomputers PC1 to PC4 shown in FIG. 1. While images corresponding to theimage data output from the computers PC1 to PC4 are being displayed onthe divided sections, the user issues an instruction, by using a remotecontroller (not shown), to switch the images one after another in thefollowing manner.

When such an instruction is issued, the projector 30 judges in step S110that the system is running in the split display mode and it alsorequests all the computers PC to suspend transmission in step S120. Thecomputers PC1 to PC4 judge in step S210 that there is a request forsuspension of transmission, and it suspends transmission in step S220.In other words, there occurs a situation in which output data from thecomputers PC1 to PC4 is absent on the network temporarily. Moreover, instep S130, the projector 30 requests the computer PC1 to transmit imagedata for one image. In step S230, the computer PC1 judges that there isa request for transmission of image data for one image, and it transmitsthe necessary image data in the form of a plurality of packets.

After the image data output from the computer PC1 has been transmitted,the projector 30 requests the computer PC2 to transmit image data forone image in step S130. In step S230, the computer PC2 judges that thereis a request for transmission of image data for one image, and ittransmits necessary image data for one image in the form of a pluralityof packet. Each packet is schematically shown in FIG. 4. It is to benoted that there exists no situation in which two packets are outputsimultaneously, one representing the image data output from the computerPC1 and the other representing the image data output from the computerPC2. Thus, the packets are transmitted sequentially.

In general, if the computer PC1 and the computer PC2 output datasimultaneously, the latter tries to output packets while the former istransmitting packets. When the packets from the computer PC1 areadequately received by the projector 30, the network load is reduced. Inthis situation, the packets from the computer PC2 are transmittedbetween the packets from the computer PC1. Then, the computer PC1 waitsfor transmission and tries to output packets. This processing usuallypermits a plurality of computers PC to transmit data simultaneously.However, data transmission in this manner results in an increasednetwork load because of the necessity for establishing connection manytimes and inquiring whether data transmission is possible or not.

Particularly, in the case of transmitting image data of large volume,transmission of image data is slow even though the receiver of imagedata (the projector 30 in this embodiment) has surplus resources, andhence the processing in the receiver of image data does not proceedsmoothly. In this embodiment, however, image data is transmittedsequentially from each of the computers PC as shown in FIG. 4; thiskeeps the network load low and permits high-speed transmission ofnecessary data. Transmitting data in this manner is advantageous overtransmitting data simultaneously from computer PC1 and computer PC2 inthat time required from the start of transmission to the end oftransmission is short for the same amount of data.

In the sequential display mode shown in FIG. 5, the user can switch, atany stage, by means of the above-mentioned remote controller, the imagesbased on the image data output from the computers PC1 to PC4 shown inFIG. 1. In other words, as shown in FIG. 5, while the image based on theimage data output from the computer PC1 is being displayed, the user canswitch that image to another image based on the image data output fromthe computers PC2 to PC4. However, while the image based on the imagedata output from the computer PC1 is being displayed, other computersPC2 to PC4 are asked to suspend transmission; therefore, there is nopossibility that the computers PC2 to PC4 and the computer PC1 outputimage data simultaneously.

In other words, the projector 30 judges in step S110 that it is runningin the sequential display mode, and it also requests in step S140 thatthe computers except for PC1 suspend transmission. The computers PC2 toPC4 judge in step S210 that there is a request to suspend transmissionand suspends transmission in step S220. It also continues the processingthat follows step S200 and waits until it receives a request fortransmission. Moreover, in step S150, the projector 30 sends thecomputer PC1 a request for transmission of image data for one image orcontinuous transmission of image data. In step S230 or S250, thecomputer PC1 judges that there is a request for transmission, and ittransmits the image data for one image or serial images in the form of aplurality of packets.

The above-mentioned processing performs control in such a way that whilethe image based on the image data output from the computer PC1 is beingdisplayed, the other computers PC2 to PC4 do not output image data. Whenthe user issues, by means of the remote controller, an instruction toswitch the source of image transmission, thereby causing the image ofimage data output from the computer PC 2 (for example) to be displayed,then the projector 30 instructs the computers (except for computer PC2)to suspend transmission in step S140 and performs the same processing asmentioned above. Thus, the projector 30 can display the image based onthe image data output from the computer PC2. Also, the computers PC1,PC3, and PC4 do not output image data in compliance with the instructionto suspend transmission. Therefore, only the image data necessary forimage display is output over the network; this reduces the network loadat all times. Moreover, since the projector acquires the necessary imagedata sequentially, it does not need a large storage capacity.

(5) Other Embodiments

The above-mentioned embodiment is intended to realize the imagedisplaying system, image displaying device, image data outputtingdevice, image displaying method, image displaying program, and imagedata outputting program. Needless to say, the embodiment may beconstructed in other manners than mentioned above. For example, theimage displaying device is not restricted to the projector; instead, itmay be a PDP, CRT, or LCD (liquid crystal display). The displayingdevice for presentation should preferably be one which has a largescreen. However, the use of the present invention is not restricted topresentation. The present invention may be applied to a monitor systemto display images taken by a plurality of cameras on a split screen, ora monitor system to sequentially display images taken by a plurality ofcameras which are switched one after another at certain time intervalsor according to the user's instruction.

Moreover, the split display mode does not necessarily require equallydivided screens as shown in FIG. 4. Instead, the screen may be dividedinto a large main section and a plurality of small sections. In thiscase, the large main section displays an image for the main subject ofpresentation that attracts the attention of audience and the smallsections display images (data) to supplement presentation. Thisarrangement will facilitate effective presentation. The content ofdisplay in the large and small sections may be switched over dependingon situation.

Moreover, the embodiment of the present invention is not restricted inthe form of network so long as the image displaying device and theterminals are connected with each other through a network. Connectionmay be by a LAN (as mentioned above) or the Internet. In this way, theuser may perform presentation by using images offered by those who areaway from one another. Both wire network and wireless network areacceptable.

In addition, the above-mentioned construction designed to select thesplit display mode and the sequential display mode is not essential. Theprojector will work in either of the two modes. The mode may be judgedfrom the image structure being used or the number of computers PCassociated with the images. (It is not always necessary to rely upon thepreviously established mode.) There are several methods for judging instep S100 the number of computers PC with established connection. Itwould be possible to count the number of the computers PC which haveresponded to broadcast communications. It would also be possible tocount the number of the computers PC which has requested connection bymemorizing that there has been a request for connection from thecomputer PC. The communication protocol is not restricted to TCP; it maybe UDP or any other protocol.

1. An image displaying device which is connected with a plurality ofterminals to store image data through a network that permits two-waycommunications and which acquires image data from each terminal, therebydisplaying an image, said image displaying device comprising: acommunication unit at the displaying device side that performs two-waycommunications with each of said terminals, an image data acquisitioncontrolling unit that acquires image data from a relevant terminal insuch a way that when the image data acquisition controlling unitacquires image data from the relevant terminal by controlling saidcommunication unit at the displaying device side, the image dataacquisition controlling unit instructs other terminals to suspendtransmission, thereby suspending transmission of image data, an imagedisplaying unit that displays an image in response to the image dataacquired as the result of control by said image data acquisitioncontrolling unit, and a mode switching unit that switches a splitdisplay mode to and from a sequential display mode, so that, in thesplit display mode, the image displaying unit displays images based onindividual image data on divided sections of one screen, and in thesequential display mode, the image displaying unit displays one imagebased on the individual image data on a full screen, wherein the imagedata acquisition controlling unit controls, in the sequential displaymode, the communication unit at the display device side in such a waythat the image data acquisition controlling unit designates a specificterminal as the relevant terminal until the transmission terminal isswitched and continues to acquire image data, and the image dataacquisition controlling unit sends to the terminals, other than therelevant terminal, a request to suspend transmission, requests therelevant terminal for transmission of image data for one image orcontinuous transmission of image data until an instruction to switch thesource of image transmission is issued, so that while the image based onthe image data output from the relevant terminal is being displayed, theother terminals do not output image data, and thereafter requests theswitched terminal to transmit image data.
 2. The image displaying deviceas defined in claim 1, in which the image data acquisition controllingunit controls, in the split display mode, the communication unit at thedisplay device side in such a way that it designates sequentially eachterminal which stores image data for images to be displayed on thedivided sections as the relevant terminal and sequentially acquiresimage data for images to be displayed on the divided sections.
 3. Animage displaying method for causing each terminal of a plurality ofterminals to output image data to an image displaying device to displayan image, thereby displaying an image, said image displaying devicebeing connected through a network capable of two-way communications withthe plurality of terminals to store image data for images to bedisplayed, said image displaying method comprising: an instruction tosuspend transmission of image data issued to other terminals when imagedata are acquired from a relevant terminal, the outputting of image datais suspended in the terminal to which an instruction to suspendtransmission has been issued, the outputting of image data is continuedin the relevant terminal to which no instruction to suspend transmissionhas been issued, the image displaying device acquires image data fromthe relevant terminal, thereby displaying images based on the acquiredimage data, switching a split display mode to and from a sequentialdisplay mode, so that, in the split display mode, the image displayingdevice displays images based on individual image data on dividedsections of one screen, and in the sequential display mode, the imagedisplaying device displays one image based on the individual image dataon a full screen, designating, in the sequential display mode, aspecific terminal as the relevant terminal until the transmissionterminal is switched and continues to acquire image data, andinstructing the relevant terminal to transmit image data for one imageor continuously transmit image data until an instruction is issued toswitch the source of the image transmission, thereby while the imagebased on the image data output from the relevant terminal is beingdisplayed, the other terminals do not output image data, and thereafterrequests the switched terminal to transmit image data.
 4. Acomputer-readable medium storing an image displaying program to controlan image displaying device which is connected through a network capableof two-way communications with a plurality of terminals to store imagedata and which acquires image data from each terminal, therebydisplaying images, said image displaying program comprising: acommunication function allowing a computer at the display device side toperform two-way communications with said terminals, an image dataacquisition controlling function which, when acquiring image data from arelevant terminal by controlling said communication function at thedisplay device side, instructs other terminals to suspend transmission,thereby suspending transmission of image data, and acquires image datafrom the relevant terminal, an image displaying function that causes theimage display device to display images based on the image data acquiredby control by the image data acquisition controlling function, and amode switching function that switches a split display mode to and from asequential display mode, so that, in the split display mode, the imagedisplaying function displays images based on individual image data ondivided sections of one screen, and in the sequential display mode, theimage displaying function displays one image based on the individualimage data on a full screen, wherein the image data acquisitioncontrolling function controls, in the sequential display mode, thecommunication function at the display device side in such a way that theimage data acquisition controlling function designates a specificterminal as the relevant terminal until the transmission terminal isswitched and continues to acquire image data, and the image dataacquisition controlling function sends to the terminals, other than therelevant terminal, a request to suspend transmission, requests therelevant terminal for transmission of image data for one image orcontinuous transmission of image data until an instruction to switch thesource of image transmission is issued, so that while the image based onthe image data output from the relevant terminal is being displayed, theother terminals do not output image data, and thereafter requests theswitched terminal to transmit image data.